Trim element

ABSTRACT

The invention relates to a trim element. It relates to a trim element having a visible side ( 12 ) formed of a skin ( 10 ), the element comprising a skin ( 10 ) laid on a plastic foam ( 24 ) bonded to the skin by a continuous bonding layer ( 26 ) formed spontaneously at the skin-foam interface during the foaming operation, the skin ( 10 ) having a preferential rupture initiator comprising at least one scored feature. Throughout the region in which the scored feature lays, the bonding layer ( 26 ) is in contact only with the skin ( 10 ) and the foam ( 24 ), and, at the scored feature and in the direction of the thickness of the skin, the bonding layer ( 26 ) is laid over the opening with a thickness very much smaller than the depth of the scored feature. Application to the interior trim of motor vehicles.

The invention relates to a trim component, substantially for theinterior trim of a motor vehicle, having a visible face which is formedby a skin which is arranged on a layer of plastics material foam, and adevice which is intended to form the notches in the skin for a trimcomponent and a method for producing a trim component.

Such trim components are used in order to form a specific number ofsurfaces, and in particular surfaces below which airbags are concealed.In this application, it is commonplace to delimit, in the skin of thecomponent covering the airbag, a notch which delimits a portion which isintended to separate, the skin tearing along the length of the notchwhen the airbag is operated.

It has been found that, in this application, a given number of tearfaults were observed along the notch. These faults were attributed tothe fact that, when the trim component is formed by means of foaming aplastics material in contact with the skin, the plastics materialpenetrates into the notch and forms a practically continuous bridge overat least a significant portion of the depth of the notch. The notchtherefore loses its functionality, since the connection provided by theplastics material between the two sides of the notch may be stronger theone which the material of the skin itself would provide without a notch.

Attempts have therefore been made to overcome this problem and it hasthus been proposed, in document DE-298 21 409, to close the opening ofthe notch, at the side of the foam, by applying a “protective lacquer”which is intended to form a bridge on the notch and thus prevent theplastics material of the foam from penetrating into the notch.

This method has the disadvantage of requiring a specific operation forforming a bridge on the opening of the notch, in a specific operationwhich is additional to the other production steps. Furthermore, thecomponent obtained must have a closure bridge which both has a low levelof strength so as not to impede the tearing of the skin when an airbagis operated and is also sufficiently strong to withstand the varioushandling operations between the production thereof and the foamingoperation inside a mould.

The object of the invention is to solve the above-mentioned problem in amanner which requires no additional production operation and thereforeno increase in cost.

More precisely, according to the invention, the notch is provided with aconfiguration which prevents the formation of a bridge of extendedthickness between the two sides of the notch. In a first shape, theconfiguration of the notch delimits an opening which is so narrow that,taking into account the wetting and surface tension properties of theskin and the plastics material used to shape the foam, the fluidplastics material practically does not penetrate into the notch. In asecond shaper the notch is open to such a wide extent that the plasticsmaterial penetrates and the plastics material foam with a low level ofstrength is what fills the space of the notch and practically does notreduce the suitability of the notch for forming a preferred breakingzone.

More precisely, the invention relates to a trim component which has avisible face which is formed by a skin, the component being of the typecomprising a skin which is arranged on a foam of plastics material, thefoam being connected to the skin by means of a continuous connectionlayer which is formed spontaneously at the skin/foam interface duringthe operation for foaming the fluid plastics material in contact withthe skin, the skin having a preferential breakage device which comprisesat least one notch which opens via an opening at the side opposite thevisible face; according to the invention, practically in the whole ofthe zone in which the notch is located, the connection layer is incontact only with the skin and the foam and, in the region of the notchand in the direction of the thickness of the skin, the connection layeris arranged on the opening with a thickness which is very much less thanthe depth of the notch.

In a first embodiment, the opening of the notch at the face of the skinhas a width which is at the most in the order of magnitude of thethickness of the connection layer. In this instance, the expression“order of magnitude” indicates a variation of between approximately 0.2and 5 times, the width of the notch still remaining very much smallerthan the depth of the notch.

In one example, the notch has its smallest width practically at theopening or in the region of the opening, so that the plastics materialpractically does not penetrate into the notch. In another example, oneside of the opening of the notch carries a blocking member which coversthe opening. In another example, in the portion adjacent to the opening,the notch has a smaller width than at a location which is further awayfrom the opening of the notch. In another example, the notch has asinuous shape in cross-section. In another example, the notch isinclined in cross-section relative to the face opposite the visibleface.

In a second embodiment, the opening of the notch at the face of the skinis sufficiently wide for the plastics material to penetrate and form afoam inside the notch, the connection layer following the inner surfaceof the notch as far as a location remote from the surface of the skin.In one example, in the region of the opening, the notch has, incross-section, a V-shape having an angle greater than 45°.

In a third embodiment, which combines the first two, the notchcomprises, from the opening, a very wide opening portion which allowsthe penetration of the plastics material, then a deeper and narrowerportion into which the plastics material practically does not penetrate.

In one example, the edges of the opening have a projection.

The invention also relates to a device which is intended to form thenotches in the skin of a component according to the above paragraphs,comprising a robot arm and a blade, in which the blade has across-section which is adapted to the cross-section of a notch to beformed, the robot arm moving the blade along a notch to be formed. Inone example, the device further comprises a mould for supporting theskin which is locally rounded at locations provided for the notch.

The invention also relates to a method for producing a trim componentaccording to the above paragraphs, in which a step for producing theskin involves arranging the skin on a mould which has a projection alongthe path desired for the notch, and cutting the notch by moving a cutterwhich has a cross-section which is adapted to the cross-section of thenotch to be produced, then separating the skin and the mould.

Other features and advantages of the invention will be better understoodfrom a reading of the following description, given with reference to theappended drawings, in which:

FIG. 1 is a cross-section through a notch formed in a skin in accordancewith the conventional method;

FIG. 2 is a section through a portion of a trim component formed withthe skin illustrated in FIG. 1 and illustrating the manifestation of theproblem solved by the invention;

FIGS. 3, 4, 5 and 6 illustrate four examples of the invention in thefirst embodiment thereof;

FIGS. 7, 8, 9 and 10 illustrate notches in examples combining two formsof the invention;

FIGS. 11 and 12 are sections illustrating notches in other examples ofthe invention corresponding to the second embodiment of the invention;and

FIG. 13 is an example of a cutter which is used to form the notch of theembodiment of FIG. 12.

FIG. 1 is a cross-section through a skin at the location of a notch.More precisely, a skin 10 having a visible face 12, having, for example,a grain, also has an inner face 14 on which a notch 16 opens via anopening 18. The notch has a V-shape which is delimited by two sides 20and 22.

When an interior trim component is produced with this skin whichdelimits one side of a moulding cavity, a plastics material which isintended to form a foam is introduced at the side of the inner face 14of the skin 10. Since the opening 18 of the notch is relatively large,the fluid plastics material can easily penetrate practically as far asthe base of the notch. When the foaming operation is complete, theinterface between the foam 24 which is normally flexible, and the innersurface 14 of the skin comprises a connection layer 26 which practicallyforms no foam and which constitutes a type of continuous film which ispractically in constant contact with the inner surface 14 of the skin.However, the plastics material which has been able to penetrate into thenotch 16 prior to the foaming operation forms a portion 28 whichcomprises only a small number of cavities and which constitutes a typeof adhesive bridge over practically the entire depth of the notch.Whilst the foam has a low level of tear-resistance owing to the porositythereof, the plastics material with a small number of cavities incontrast has a high level of tear-resistance.

Even if the plastics material does not penetrate into the entire depthof the notch but instead only over a third or a half, it forms a bridgewhich is sufficiently strong for the notch, after polymerisation andcooling, not to have a level of strength which is very much less thanthat of the skin itself which surrounds it. The notch therefore nolonger necessarily constitutes a preferred breaking device owing to thisconnection between the two sides 20, 22 of the notch.

The solution to this problem is to prevent the plastics foaming materialfrom penetrating into the notch, as suggested by the above-mentioneddocument of the prior art.

It is possible to envisage the use of a very thin aperture but it is noteasy to simply reduce the width of the notch. The notch is normallyproduced by means of pressure and it is not possible to produce notchesof very small width since the blades used must be so thin that they haveno durability.

According to the invention, in order to prevent the fluid plasticsmaterial from penetrating into the notch, the notch is provided withsuch a configuration that the connection layer formed by the plasticsmaterial may only form, between the two sides of the notch, a bridgewhich is very thin and which therefore has a low level of strength. Thisbridge may be located either close to the inner face of the skin, in theregion of the opening, or at the base of the notch, or in anintermediate position.

In the embodiments of FIGS. 3, 4, 5 and 6, the bridge formed by theconnection layer is close to the inner surface of the skin. In theembodiments of FIGS. 11 and 12, the bridge formed by the connectionlayer is located at the base of the notch. In the embodiments of FIGS.7, 8, 9 and 10, this bridge is located in an intermediate position.

FIGS. 3 to 6 illustrate embodiments in which the opening of the apertureat the inner surface 14 is very small, so that the connection layer 26practically does not penetrate into the notch which remains empty.

In the embodiment of FIG. 3, the notch is very fine so that the openingthereof is very small and it is inclined in a direction opposed to theflow direction 33 of the plastics material which is injected in order toform the foam layer. In this manner, the fluid plastics material doesnot have a tendency to penetrate into the notch 32.

In the embodiment of FIG. 4, the notch 34 has a bent shape so that itdelimits, in the region of the opening, a blocking member 36 whichpractically closes the opening so that the fluid plastics material whichforms the connection layer 26 cannot penetrate into the notch.

In the embodiment of FIG. 5, the notch 38 has a sinuous shape and asmall opening so that the fluid plastics material which forms theconnection layer 26 terminates at the opening. If the plastics materialhad a tendency to penetrate locally into the notch 38, the sinuous shapewould reduce the penetration thereof.

FIG. 6 illustrates an embodiment in which the notch 40 has, at the sideof the inner face, a very small opening which is formed by a notchportion 42 which prevents the fluid plastics material of the connectionlayer 26 from entering. However, towards the inner side of the skin, thenotch has a wider portion 44 which may increase the breaking properties.

FIGS. 11 and 12 illustrate the second form of the invention. In theseFigures, the notch is open so wide that the fluid plastics material isable to penetrate as far as the base, forming a thin connection layer 26on the walls of the notch. The width of the notch is such that theplastics material forms foam almost as far as the base of the notch. Asa consequence, the bridge formed between the two walls of the notch bythe connection layer 26 exists only at the base and has a smallthickness. This bridge therefore has only a low level of resistance tobreaking.

In the embodiment of FIG. 11, the notch 76 is symmetrical and, in theembodiment of FIG. 12, the notch 80 is asymmetrical so that one side ofthe notch 80 is practically perpendicular relative to the skin and theother is greatly inclined, for example, through an angle of 45°. Theeffect obtained during a breakage may thus be asymmetrical and promotethe separation of the portion which must be broken away.

FIGS. 7 to 10 illustrate embodiments in which the two forms of theinvention are combined. More precisely, the notches of these embodimentscomprise, towards the inner surface 14, a wide portion which has theeffect described with reference to the FIGS. 11 and 12 and, towards thebase, a narrow portion such that the opening has a small width whichprovides the phenomenon described with reference to FIGS. 3 to 6.

The embodiment of FIG. 7 has a notch 46 which comprises an outer portion48 which is open to a large extent and whose function is similar to thatdescribed with reference to FIG. 11. The narrowest inner portion of thisnotch portion 48 is connected via a narrow opening to a second narrownotch portion 50. The bridge formed by the connection layer is limitedto one narrow portion in the region of the connection between the twoportions 48 and 50 of the notch 46.

In the embodiment of FIG. 8, there is further indicated the presence ofprojections 58 around the outer notch portion 54 that is connected to anarrow inner portion 56 in the notch 52. These projections 58 are formedwhen the tool used to form the notch is of the heating type, so that aflange such as 58 (FIG. 8, 66 (FIG. 9), 74 (FIG. 10), 78 (FIG. 11) isformed around the opening at the inner face.

In the embodiment of FIG. 9, the notch 60 has an outer portion 62 whichis similar to that of the embodiment of FIG. 8, and an inner portion 64which widens after a narrow opening, as in the embodiment of FIG. 6.

The embodiment of FIG. 10 is similar to that of FIG. 8 and comprises anotch 68 having a wide portion 70 at the side of the inner surface and anarrow portion 72 at the side of the visible face. Compared with theembodiments of FIGS. 7 to 9, in which the notch portion close to theinner surface 14 has a V-shape in cross-section, the notch portion 70 isdistinguished by a bell-like shape which allows the thickness to bereduced for the bridge which is formed at the opening of the inner notchportion 72, compared with the embodiments of FIGS. 7 to 9.

It has been indicated above that the production of an aperture which isvery thin as illustrated in FIG. 3 or which has a portion which islocally very thin as indicated in FIGS. 6 and 9 presented problems. Theconventional technique used during the production of the skin does notallow such configurations to be readily produced, in particular sincethe equipment has only a low level of durability.

According to the invention, this problem is resolved owing to a specificmethod and device.

In this manner, in a method for producing such notch configurations, thenotches are not formed by means of pressure or moulding, but instead bymeans of cutting using cutters of an appropriate shape which arepreferably moved by means of a robot.

Of the various embodiments of notches, the notch shapes of FIGS. 6 and 9are the ones which present the greatest problems in terms of productionowing to the variation in the width of the opening towards the base.FIGS. 6A and 9A are diagrams indicating how these notches which are themost difficult to produce are formed.

As indicated in FIGS. 6A and 9A, at the location at which the notch mustbe produced, the skin is placed on a highly-curved support 82, and acut-out is produced using a cutter which has a cross-section having ashape which is adapted to that of the notch widened on the mould. Inthis manner, although the inner portion 44 of the notch is wider thanthe outer portion 42 in a position for use (FIG. 6), it will be noted inFIG. 6A that, during production, the notch has a width which decreasescontinuously from the outer side towards the inner side and which cantherefore be produced readily with a strong cutting blade. In FIG. 6A,the outer notch portion 42 is intended to form a portion havingpractically parallel walls (FIG. 6) whilst, in the embodiment of FIG. 9,the outer notch portion 66 is intended to delimit a portion open to awide extent.

FIG. 13 is a cross-section, by way of example, through a blade which canbe used for the cutting formation of the notch 80 illustrated in FIG.12. This cutting blade, only the tip of which indents the skin, mayoptionally be heated and, in this instance, it forms a flange asindicated by the reference numeral 84 in FIG. 12.

In this manner, the invention relates to a device which is intended toform notches of the type described, in which a robot moves a bladehaving a cross-section which is adapted to the cross-section of thenotch to be formed, optionally on a skin which is placed on a mouldwhich is locally rounded opposite the notch.

The invention also relates to a method for producing a trim component ofthe type in question in which the production of the skin involvesarranging the skin on a mould which has a projection which follows thepath desired for the notch, and cutting the notch using a cutter havinga cross-section which is adapted to the cross-section of the notch to beproduced, then separating the skin and the mould.

1. A trim component which has a visible face which is formed by a skin,the component comprising: a skin which is arranged on a foam of plasticsmaterial, the foam being connected to the skin by means of a continuousconnection layer which is formed spontaneously at the skin/foaminterface during the operation for foaming the fluid plastics materialin contact with the skin, the skin having a preferential breakage devicewhich comprises at least one notch which opens via an opening at theside opposite the visible face, wherein, substantially in the whole ofthe zone in which the notch is located, the connection layer is incontact only with the skin and the foam and, in the region of the notchand in the direction of the thickness of the skin, the connection layeris arranged on the opening with a thickness being less than the depth ofthe notch, wherein the opening of the notch at the face of the skin hasa width which is at the most 0.2 and 5 times the thickness of theconnection layer, the notch has its smallest width at the opening or inthe region of the opening, the notch being substantially free of thefluid plastics material penetrating therein.
 2. The trim componentaccording to claim 1, wherein, in the portion adjacent to the opening,the notch has a smaller width than at a location which is further awayfrom the opening of the notch.
 3. The trim component according to claim1, wherein the notch has a shape which is selected from a shape which issinuous in cross-section and a shape which is inclined in cross-sectionrelative to the face opposite the visible face.
 4. The trim componentaccording to claim 1, wherein the edges of the opening have aprojection.
 5. A method for producing a trim component according toclaim 1, comprising the steps of: arranging the skin on a mould whichhas a projection which follows the path desired for the notch, cuttingthe notch using a blade having a cross-section corresponding to thecross-section of the notch to be produced, separating the skin and themould, forming the foam of plastics material against the skin.
 6. Themethod according to claim 5, comprising the step of heating the bladeprior to forming the notch.
 7. A trim component which has a visible facewhich is formed by a skin, the component comprising: a skin which isarranged on a foam of plastics material, the foam being connected to theskin by means of a continuous connection layer which is formedspontaneously at the skin/foam interface during the operation forfoaming the fluid plastics material in contact with the skin, the skinhaving a preferential breakage device which comprises at least one notchwhich opens via an opening at the side opposite the visible face,wherein, substantially in the whole of the zone in which the notch islocated, the connection layer is in contact only with the skin and thefoam and, in the region of the notch and in the direction of thethickness of the skin, the connection layer is arranged on the openingwith a thickness being less than the depth of the notch, wherein thenotch comprises, from the opening towards the visible face, an outerportion having a first opening angle that opens towards the sideopposite the visible face and is filled with the plastics material, aninner portion having a second opening angle that opens towards the sideopposite the visible face and being substantially free of penetration bythe plastics material, and wherein a width at the opening of the firstopening angle is sufficiently greater than a width at the opening of thesecond opening angle for the plastics material to penetrate and form thefoam.
 8. A trim component which has a visible face which is formed by askin, the component comprising: a skin which is arranged on a foam ofplastics material, the foam being connected to the skin by means of acontinuous connection layer which is formed spontaneously at theskin/foam interface during the operation for foaming the fluid plasticsmaterial in contact with the skin, the skin having a preferentialbreakage device which comprises at least one notch which opens via anopening at the side opposite the visible face, wherein, substantially inthe whole of the zone in which the notch is located, the connectionlayer is in contact only with the skin and the foam and, in the regionof the notch and in the direction of the thickness of the skin, theconnection layer is arranged on the opening, wherein the notchcomprises, from the opening towards the visible face, an outer portionhaving a first opening angle that opens towards the side opposite thevisible face and is filled with the plastics material, an inner portionhaving a second opening angle that opens towards the side opposite thevisible face and being substantially free of penetration of the plasticsmaterial, wherein a width at the opening of the first opening angle issufficiently greater than a width at the opening of the second openingangle for the plastics material to penetrate and form the foam, andwherein the edges of the opening have a projection being located in theouter portion of the notch.